carb question

[RamMedic]

Ok, so we discussed pistons. Now lets talk carbs. Lets just say for discussion: Stock twinkie bottom end, 95 flat top pistons, 510 cams. Where would one go with a carb. Keep the stock CV or change to ???????(insert brand). Increase size or keep the same? Intake????? The floor is open for discussion. :mrgreen: (keep the heads out of it, we can discuss them next :mrgreen: )

[speed]

44mm Mikuni like big Pat's. Your proposed setup is virtually the same as his and he made an extra 4HP and 6 pounds of torque on the dyno going to the bigger Mikuni.

SM

[CoolMaker]

Stock Harley....

[Fubar]

I know you said keep the heads out of it, but if you plan on doin the heads then Speed is right no? you should go to a larger Carb

I mean I've ridden with you, and you like to twist the wick at higher rpms, and at those rpms you'll see the stock CV will let you down....

Weather you go with S&S or Mikuni is up to you....they have different technologies both are proven....I prefer the S&S, because it is so easy to work on and tune....and tuning is EVERYTHING...don't mean shit if its; bigger if you can't tune it correctly....hell the Mikuni could be the same, but I have experience only with the S&S
Speeds obvioulsy talking from experience, with similar mods...I know every bike is different but, I generally follow the experince...road once traveled and all that ...plus if your gonna do the heads eventually....then well you know he's probably even more right....

[wrecker]

have to agree with fubar on this one

[speed]

Mikuni versus S&S - six to one, half a dozen to another. The only reason we went Mikuni on Pat's bike is because virtually all snowmobiles used to have Mikuni carbs before the industry went EFI and we are all exceptionally familiar with them.

For comparison's sake ...

Pat's 1999 Road King made 94HP and 98 pounds of torque on the dyno with the following setup:

95" inch big bore kit - same as you are considering.

Flat top HD pistons w/ 9:1 compression ratio - same as you are considering.

S&S 510G cams - same as you already have.

Screaming Eagle ignition - same as you already have.

Stock heads - perhaps the same as you are considering for budgetary purposes.

44mm Mikuni carb - directly answers your question in this thread based on experience and time on the dyno. Speaking of which, I personally tuned the carb on his bike.

Samson long shot drag pipes - not even remotely similar to your 2 into 1 Thunder header, which by all rights should make more power than his pipes. On that topic look at the torque we made with Pat's bike - 98 freakin' pounds with drag pipes and no head work. That number was 92 pounds without the big carb and everything else being the same, so take it for what's it's worth.

SM

[softail]

OK, so you can increase the port velocity with a smaller carb, but limit (restrict flow) at high rpm's when she needs the most air intake. At what point on the rpm's did you gain the extra hp/tq? Was it in the lower or top end?
When my bitch was still just a wee little 95", I found myself twisting her neck all the time in order to feel the power that engine was producing. With my current build, I have a tq peak that starts at 3K with 140+ ft lbs and hits 153 at 4K. I don't need to twist the neck all the time with this build.
I know, different subject, but port velocity at lower rpm's helps with the low end grunt. Correct? So, just to confuse the shit out of you. Wouldn't you want the best of both worlds? I had a mikuni hsr42 on my 95 that held me back to 93 hp and 105 tq. I added a set of (Really open 2-1 drag pipes) RBR LSR Pro Stock, and found the carb almost untunable, fuck, completely untunable for that pipe. I then found myself talking to
J. Wagner, and he felt that since the Mik had no high speed air jet, I might want to look at an S&S E or G, but both carbs would have to big of a throat I.D. for the little 95" so I should look at the Davinci booster. The other problem with both the Mik and the S&S was the length of the carb from intake to manifold, thus shortening the plenum. With the cam overlap I had. I was getting some real bad reversion issues that were causing a serious flat spot at 2800-3200. The fact that the S&S had an air bleed that was changeable, was supposed to help out, and solve the situation. It didn't. I tried several different boosters. I tried every jet combo I could, and finally was able to get the most out of the little bitch. It was never equal to the bang for the buck the Mik gave me before I started to fuck with all that shit.

Now that I have the 124" the carb is just the right size. She still took some tuning, and several calls to Jon. The end result was great, but in hind site. The 95" was at her best with the 2-2 Rineharts and the tiny little HSR42.

Hey cool, what happened to your ride when you went to the bigger throttle body? No slam intended, but did you gain hp up high and loose something (Hp/Tq) down low? I never saw the dyno after the change, but had heard that the expected results were not achieved. What ever did you wind up doing, and what was the final numbers?

The answer to the question: IMHO Mikuni HSR42 has great throttle response.

Now that I have my S&S G (That is bored out to 52mm) with a Davinci booster totally tuned to the friggin max, and my bud has a HSR 42 on his 88" stage one, I think the S&S is more responsive. Unfortunately the S&S satisfaction came with a huge price, and not dollars, but patience with tuning.

The other new carb on the block is the Genisis big air carb. It has a triangle shaped throat with a flat slide that gives a minimal opening at low rpm's, opens the fuck up at W.O.T. givving the best of both worlds. The problem that I see with this carb is.
1. Only one cable
2. It comes from the snow sled market, and is new to street bikes. It would require some interesting fab work to install.
3. I know very little about it, and don't want to drop the grand just for a try and see. :roll: I've done that shit before with results very different from the sales persons.

Maybe Bigshovel could join in and help with this topic.

Cheers.


<EDIT>

High speed air bleed or jet... Allows you to move the main circut up and down the rpm range to avoid extra gas during the reversion pulses.

Davinci booster is a bomb sight looking venturi that installs in the S&S E or G's throat to increase signal at low rpm's. (Some people swear by them)

The Mik is short for Mikuni, and the Mik's have eliminated the high speed air bleed. They have a blank plug that look like you could drill it out, but behind the plug is a blocked passage.

I belive that the S&S E and especialy the G are to big of a carb for the 95" build without a booster venturi installed, and the G, even with the booster is to big period. The 45 could very well be to much carb for the 95". Take a look at the dyno charts for the 95" builds on the Headquarters web site. The numbers the HSR42 are fucking killer.

www.head-quarters.com

<EDIT2>

Here is one that proves it.

http://www.head-quarters.com/html/116_x_118.html